Local switching networks (e.g., a switching network contained within an office building) may include a switching fabric connecting end devices via line cards. The term end devices is defined in this specification to include desktop computers, printers, routers or other networking equipment etc. FIG. 1 illustrates, in block diagram form, an exemplary local switching network 100. Local switch network 100 includes a switching fabric 102 (e.g., a cross bar switching fabric) coupled to line cards 104–108. Each of the line cards may include one or more ports which, in turn, may be coupled to end devices or other networks. FIG. 1 shows line card 106 coupled to four end devices 110–116, line card 104 coupled to end device 118, and line card 108 coupled to end device 120.
Line card 106 shown in FIG. 1 includes a pair of end device ports embodied in port application specific integrated circuits (ASICs) 122 and 124. The port ASICs 122 and 124 are coupled to end devices 110–116 and to switching fabric 102 via interface and local switch 126. Port ASICs 122 and 124 are coupled to interface and local switch 126 via a shared bus 128. Moreover, interface and local switch 126 is coupled to switching fabric 102 via data link 130. Line cards 104 and 108 are likewise coupled to switching fabric 102 via data link 132 and 134, respectively.
The local switching network 100 shown in FIG. 1 may employ one of many different communication protocols enabling data communication between one or more end devices 110–120 via line cards 106 through 108 and switching fabric 102. FIG. 1 will be described with reference to a communications protocol in which end devices communicate by transferring variable sized data frames with headers including source and destination information. Communication between end devices 110–120 can occur via a stream of such variable frames transmitted therebetween.
FIG. 2 illustrates an exemplary frame 200 used in the network 100 shown in FIG. 1. More particularly, frame 200 includes a header which further includes: field 202 containing a source IP address of one of the end devices 110–120; field 204 which contains a port number associated with the source IP address; field 206 which contains a destination IP address of an end device to receive frame 200, and; field 208 which contains a port number associated with the destination IP address in field 206. Frame 200 may further include one or more fields 210 for the data payload.